Food Allergy 102: Testing for Food Allergies

Do You Have A Food Allergy? Check out this post.

Responses to food allergies can be quite variable from individual to individual. It may involve gastrointestinal reactions including nausea, abdominal cramps, vomiting, and diarrhea, itchy rash, hives, asthma and hay fever, swelling of the lips, tongue and throat, migraine headaches and in severe cases, anaphylaxis. Some cases of food-induced hives or anaphylaxis are dependent on a cofactor for exacerbation of clinical symptoms. The only cofactor clearly demonstrated to provoke symptoms is exercise.

Before one should embark on an investigation of a food allergy, there must be a reasonable suspicion of food senstivity based on the development of symptoms following the consumption of a particular food. Random testing for food allergies without one of the symptoms listed above is likely to be futile and an unnecessary medical expense. If there is a reasonable suspicion of food allergy, the first step is allergy skin testing to the suspected foods. A negative skin test result is highly accurate and can be used to reassure you that you are not allergic. On the other hand, a positive test does not confirm an allergy, but suggests that you may be allergic to the particular food. Foods to which a positive test is obtained should be eliminated from your diet for a trial period to see whether your symptoms resolve.

The only completely objective test for validating a food allergy is the double-blind placebo-controlled food challenge. In this test both the physician and patient are blinded to whether the testing substance contains placebo or food. Subjects injest either placebo or food, and then symptoms are noted for a certain period of time. These day-long testing sessions are normally only conducted at academic medical institutions.

Accurate diagnosis of food allergy is important for several reasons. Deleting suspected foods from your diet has nutritional and social implications. If a major food group is avoided, then nutritional adequacy has to be ensured.